Introduction to Biology

• Biology is the scientific study of life
• It explores the structure, function, growth, origin, evolution, and distribution of living organisms

Core Principles of Biology

• All living organisms are composed of cells, which is cell theory
• Gene theory says hereditary information is encoded in DNA and passed from parents to offspring
• Life evolves over time through natural selection
• Living organisms maintain a stable internal environment, homeostasis

Levels of Biological Organization

• Atoms combine to form molecules, such as DNA and proteins
• Cells are the basic unit of life, consisting of organelles and other structures enclosed by a membrane
• Tissues are groups of similar cells performing a specific function
• Organs are structures composed of different tissues working together
• Organ systems are groups of organs that cooperate to perform major bodily functions
• Individual living entities are organisms
• Groups of individuals of the same species living in the same area are populations
• Populations of different species living and interacting in the same area are communities
• Communities and their physical environment make up ecosystems
• All ecosystems on Earth make up the biosphere

Branches of Biology

• Biochemistry studies the chemical processes within and relating to living organisms
• Molecular biology studies the structure and function of biological macromolecules
• Cell biology studies cell structure, function, and behavior
• Genetics studies heredity and genetic variation
• Microbiology studies microorganisms, such as bacteria, viruses, and fungi
• Botany is the study of plants
• Zoology is the study of animals
• Ecology is the study of the interactions between organisms and their environment
• Evolutionary biology studies the evolutionary processes that have shaped the diversity of life

Genetic information

• Genes are units of heredity made of DNA
• DNA (deoxyribonucleic acid) contains the instructions for building proteins
• Genes are organized into chromosomes
• During reproduction, genes are passed from parents to offspring, resulting in inherited traits
• Mutations are changes in the DNA sequence that can lead to genetic variation

Evolution and Natural Selection

• Evolution is the change in the genetic makeup of a population over time
• Natural selection leads to adaptation, and is the process by which individuals with certain heritable traits survive and reproduce at a higher rate than others
• Evidence for evolution includes fossils, comparative anatomy, and molecular biology

Cell Structure and Function

• Cells are the basic unit of life
• Eukaryotic cells contain membrane-bound organelles, such as the nucleus, mitochondria, and endoplasmic reticulum
• Prokaryotic cells lack membrane-bound organelles
• The plasma membrane is a selectively permeable barrier that controls the movement of substances into and out of the cell
• Cytoplasm is the region of the cell between the plasma membrane and the nucleus, containing organelles and cytosol
• The nucleus contains the cell's DNA and controls cell activities

Metabolic Processes

• Metabolism is the sum of all chemical reactions that occur within an organism
• Enzymes are biological catalysts that speed up chemical reactions
• Photosynthesis is when plants and other organisms convert light energy into chemical energy in the form of glucose
• Cellular respiration is the process by which cells break down glucose to release energy in the form of ATP

Reproduction

• Asexual reproduction involves a single parent and produces offspring that are genetically identical to the parent
• Sexual reproduction involves two parents and produces offspring that are genetically unique
• Meiosis is a type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes as the parent cell
• Fertilization is the fusion of a sperm and egg cell to form a zygote

Ecology

• Populations are groups of individuals of the same species living in the same area
• Communities are populations of different species living and interacting in the same area
• Ecosystems are communities and their physical environment
• Biomes are large geographic areas characterized by specific climate conditions, plant communities, and animal communities

Interactions within Ecosystems

• Competition occurs when two or more species require the same limited resource
• Predation occurs when one organism (the predator) feeds on another organism (the prey)
• Symbiosis is a close and long-term interaction between two different species

Homeostasis

• Homeostasis is the maintenance of a stable internal environment in the face of external changes
• Negative feedback mechanisms are commonly used to maintain homeostasis by counteracting changes in the internal environment
• Examples of homeostatic regulation include maintaining body temperature, blood glucose levels, and blood pH

Viruses

• Viruses are infectious entities that are not considered living organisms
• They consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid)
• Viruses replicate by invading host cells and using the host's cellular machinery to produce more virus particles

The kingdoms of life

• Monera/bacteria
• Protista
• Fungi
• Plantae
• Animalia

Biology is the scientific study of life, exploring structure, function, evolution and distribution of living organisms. Key principles include cell theory, gene theory, evolution, and homeostasis. Levels of biological organization include molecules, cells, tissues, organs, organ systems and organisms.